The tripod joint of a vehicle powertrain is a component which transfers rotary power from a transmission to a shaft connected to drive wheels.
In brief, an assembly of a spider 100 and rollers 20 is inserted into a housing 10, which is connected to a transmission and rotates along therewith, and a shaft 30 is inserted into the spider 100, so that rotary power is transferred from the transmission to drive wheels, as illustrated in FIG. 1.
As illustrated in FIGS. 1 and 2, the spider 100 has trunnions which protrude at regular intervals of 120 degrees, and after the rollers 20 are coupled to the respective trunnions, the assembly thereof is inserted and assembled in the housing 10.
In this case, the spider 100 may be made of chrome-nickel alloy steel, which may be carburized to harden the surface of the spider.
A conventional spider is made of alloy steel comprising, for example, 0.17 to 0.23 wt % of C, 0.15 to 0.35 wt % of Si, 0.55 to 0.90 wt % of Mn, 0.85 to 1.25 wt % of Cr, 0.15 to 0.35 wt % of Mo, 0.030 wt % or less of P, 0.030 wt % or less of S, and a balance of Fe.
When carburizing is performed on the spider made of such a material, the surface of the spider may be hardened to have a hardness of 600 Hv to provide improved durability of the spider.
However, since parts have been recently required to have a long life, there is an increasing need for an alloy steel specialized to manufacture a spider having extended life span compared to conventional spiders, and a manufacturing method capable of controlling the surface hardness and hardening depth thereof.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.